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treadmill teardown for dummies

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  • #31
    Solved that. Now that I have only a small car and no utility trailer, I'd have to dismantle them at the curbside to bring them home. Already have more than I'm liable to use anyway!
    "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979


    • #32
      I've been a fan of dc pm motors for a long time. My main lathe is using a tm motor, my second lathe uses one to. The Unimat is using the armature from the original motor, but has been converted to permanent magnet. All the powered accessories for the lathe use dc motors. So far, every one of them runs from an ac to dc power supply with bridge rectifier and capacitor filter. Nothing is electronic yet- which might seem odd because I am an electronic technician by trade.

      The downside is that I don't get precise speed regulation- instead I get a no-load speed according to what secondary voltage I select by switch, and I use the slow down under load as an indicator instead of cursing it. The other downside is that for full power I need a relatively large and heavy transformer- and to get the multiple secondary voltages I need to rewind the secondary. I'm ok with doing that- but for most people I don't recommend it. It's very time-consuming, usually being a week long or more project, and if you want to get up to 2 hp or more, that requires a large and heavy transformer and lots of heavy magnet wire.

      One benefit I have that you won't is full isolation from the ac line. Any of the triac or scr based controls won't give you isolation, but neither does any motor running from the ac line voltage. Not a big deal I suppose.

      If you are using a tm motor that came with a choke in series, I would recommend you keep that choke in the system. It does help to keep motor noise down, and it allows for smoother running at slower speeds. Anything to keep mechanical noise off your lathe helps to keep the 'telegraphing' off your work piece. DC motors are not all the same- you can have one running in your hand and be able to feel and hear it running- or you can hand hold it and not feel it running or hear it running. Some are way smoother than others. All the treadmill motors I'm using right now are quite smooth on my power supplies- and that's without the flywheel. A proper electronic control could probably duplicate that smoothness over most speeds. But some will be noisy and prone to 'hunting' at certain speeds.

      An interesting speed control circuit that I've found in mixmasters and in one or two other applications is the mechanical governor, in which the supply voltage is fed through a set of contacts which break when the dialed in speed is reached. This is kind of a noisy thing too- and is superseded by the electronic controls you guys are talking about.

      Anyway, I'm just rambling. Down to the basement now to mop up more water.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-